Internet TV is an exciting possibility which is in its infancy. The technical quality of TV available now is remarkable, but at this stage little of it is a scheduled program such as you might recognise on your domestic TV. Take a look at Narrowstep. Sometimes this is called IPTV (Internet Protocol TV).
However there is something else that uses the same (or similar) technology, is called IPTV and is big business now. This is essentially a muli-channel cable service offered by telephone companies using their existing telephone lines and broadband technology to deliver it.
You can’t compare the two, but it is easy to get confused. The cable type service is delivered over the telephone company’s private managed network, not the global internet. Therefore they can deliver HD TV, and they can use broadcast protocols which are much more efficient.
It is important to distinguish the two and a proposed convention is to use Internet TV for Internet TV and IPTV for the cable type of service.
Bob Browning's blog 
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